Ash's Buizel was caught by Dawn but was traded to Ash because he preferred battles over contests.
Buizel gained a reputation for being a very powerful Pokemon and proved capable of defeating Dawn's Piplup, Zoey's Glameow and Ash's Pikachu. However, because he focused on strength, Buizel was unprepared for contest moves and Dawn managed to capture him.
While Ash and Dawn where preparing for their gym and contest battles, Buizel was showing more interest in what Ash was doing, than the contest, while Aipom was doing the same with Dawn's training. Ash and Dawn traded Aipom and Buizel.
Ash used Buizel against Paul's Gastrodon and won with Ice Punch. He also battled Paul's Drapion who was attacked with a powerful Pin Missile but Buizel was able to do use Water Gun Counter Shield and dodged Cross Poison. While in the air, Buizel used SonicBoom but Drapion blocked it and ensnared Buizel with its tail claw. Buizel broke free by inflating his flotation sac and then blasting Drapion with Water Gun but Drapion launched Toxic Spikes while Buizel was still in the air. As soon as he landed Buizel was poisoned by Toxic Spikes and Drapion finished him with Pin Missile.